Current Issue : October - December Volume : 2018 Issue Number : 4 Articles : 5 Articles
This paper studies the impacts of antenna selection algorithms in decode-and-forward (DF) cooperative nonorthogonal multiple\naccess (NOMA) networks, where the secure information from the relay can be overheard by an eavesdropper in the networks. In\norder to ensure the secure transmission, an optimal antenna selection algorithm is proposed to choose one best relay�s antenna to\nassist the secure transmission. We study the impact of antenna selection on the system secure communication through deriving\nthe analytical expression of the secrecy outage probability along with the asymptotic expression in the high regime of signal-tonoise\nratio (SNR) and main-to-eavesdropper ratio (MER). From the analytical and asymptotic expressions, we find that the system\nsecure performance is highly dependent on the system parameters such as the number of antennas at the relay, SNR, and MER. In\nparticular, the secrecy diversity order of the system is equal to the antenna number, when the interference from the second user is\nlimited....
An extensive area implementation of fully observed greenhouses motivates on\nresearch, especially in remote greenhouses. However, implementation of\nwireless sensor networks (WSNs) is still needed for investigation. Cognitive\nradio sensor networks (CRSNs) took advantage of using the cognitive radio\n(CR) concept to which allowed wireless sensor networks to dynamically access\ninto white space channels which is unused channels. In this paper, we adopted\nthe Generalized Implicit-OR as CRSN sensing protocol to reduce the energy\nconsumption and increase the network lifetime in multiple numbers of\ngreenhouses. Our results showed that enhanced energy consumption and improved\nnetwork lifetime compared to ordinary WSN....
The MAC (medium access control) of CSMA (carrier sense multiple access) is widely used in distributed wireless\nnetworks with random node locations. In CSMA MAC, two nodes that are within the range of one another cannot\ntransmit packets simultaneously. Modeling the concurrently transmitting nodes is crucial for the performance\nanalysis of the CSMA networks. In this paper, we study the density of concurrently transmitting nodes and propose\nanother modification of classical hard core point process to accurately estimate the density of concurrently\ntransmitting nodes, in the absence and in the presence of fading conditions. The MMHCP model we propose\noutperforms the popular Mat�©rn type II model and the existing modified hard core point (MHCP) process model by\navoiding the underestimation and alleviating the overestimation issues, respectively. We conduct extensive\nnumerical analysis and simulations to evaluate the accuracy of our MMHCP model. Furthermore, we study the\nimpact of the density of initial Poisson Point Process (PPP) and fading factor on the mean probability of successful\nreception and on the transmission capacity of networks from numerical analysis and simulations....
The wireless monitoring system is always destroyed by the insufficient energy of the sensors in railway. Hence, how to optimize\nthe communication protocol and extend the system lifetime is crucial to ensure the stability of system. However, the existing\nstudies focused primarily on cluster-based or multihop protocols individually, which are ineffective in coping with the complex\ncommunication scenarios in the railway wireless monitoring system (RWMS). This study proposes a hybrid protocol which\ncombines the cluster-based andmultihop protocols (CMCP) to minimize and balance the energy consumption in different sections\nof the RWMS. In the first hierarchy, the total energy consumption is minimized by optimizing the cluster quantities in the clusterbased\nprotocol and the number of hops and the corresponding hop distances in themultihop protocol. In the second hierarchy, the\nenergy consumption is balanced through rotating the cluster head (CH) in the subnetworks and further optimizing the hops and\nthe corresponding hop distances in the backbone network. On this basis, the system lifetime is maximized with the minimum and\nbalance energy consumption among the sensors. Furthermore, the hybrid particle swarmoptimization and genetic algorithm(PSOGA)\nare adopted to optimize the energy consumption fromthe two-layer hierarchy. Finally, the effectiveness of the proposed CMCP\nis verified in the simulation. The performances of the proposed CMCP in system lifetime, residual energy, and the corresponding\nvariance are all superior to the LEACH protocol widely applied in the previous research. The effective protocol proposed in this\nstudy can facilitate the application of the wireless monitoring network in the railway system and enhance safety operation of the\nrailway....
Comprehending unstructured text is a challenging task for machines because it involves understanding texts and answering\nquestions. In this paper, we study the multiple-choice task for reading comprehension based on MC Test datasets and Chinese\nreading comprehension datasets, among which Chinese reading comprehension datasets which are built by ourselves. Observing\nthe above-mentioned training sets, we find that ââ?¬Å?sentence comprehensionââ?¬Â is more important than ââ?¬Å?word comprehensionââ?¬Â in\nmultiple-choice task, and therefore we propose sentence-level neural network models. Our model firstly uses LSTMnetwork and a\ncompositionmodel to learn compositional vector representation for sentences and then trains a sentence-level attention model for\nobtaining the sentence-level attention between the sentence embedding in documents and the optional sentences embedding by\ndot product. Finally, a consensus attention is gained by merging individual attention with the merging function. Experimental\nresults show that our model outperforms various state-of-the-art baselines significantly for both the multiple-choice reading\ncomprehension data sets....
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